[DOC] Add documentation related to primary and replica batch allocator timeout

[imRishN]

What do you want to do?

• Request a change to existing documentation
• Add new documentation
• Report a technical problem with the documentation
• Other

Tell us about your request. Provide a summary of the request.

*Version: List the OpenSearch version to which this issue applies, e.g. 2.14, 2.12--2.14, or all.

What other resources are available? Provide links to related issues, POCs, steps for testing, etc.

[hdhalter]

HI @imRishN, is this being released in 2.16?

[Naarcha-AWS]

@imRishN: Has this update already been released as a part of 2.16?

[dblock]

[Catch All Triage - 1, 2, 3, 4, 5]